UC San Diego

Anatomic knowledge of the internal auditory canal (IAC) and surrounding structures is a prerequisite for performing skull base approaches to the IAC. We herein perform a morphometric analysis of the IAC and surgically relevant aspects of the posterior petrous bone during pediatric maturation, a region well-studied in adults but not children. Measurements of IAC length (IAC-L), porus (IAC-D) and midpoint (IAC-DM) diameter, and distance from the porus to the common crus (CC; P-CC) and posterior petrosal surface (PPS) to the posterior semicircular canal (PSC; PPS-PSC) were made on thin-cut axial CT scans from 60 patients (grouped by ages 0-3, 4-7, 8-11 12-15, 16-18, and > 18 years). IAC-L increased 27.5% from 8.7 ± 1.1 at age 0-3 to 11.1 ± 1.1 mm at adulthood (p = 0.001), with the majority of growth occurring by ages 8-11. IAC-D (p = 0.52) and IAC-DM (p = 0.167) did not significantly change from ages 0-3 to adult. P-CC increased 31.1% from 7.7 ± 1.5 at age 0-3 to 10.1 ± 1.5 mm at adulthood (p = 0.019). PPS-PSC increased 160% from 1.5 ± 0.7 at age 0-3 to 3.9 ± 1.2 mm at adulthood (p < 0.001). The majority of growth in P-CC and PPS-PSC occurred by ages 12-15. Knowledge of these patterns may facilitate safe exposure of the IAC in children.